It seems like a very interesting shift. However, the increase in ability to detect arctic thunderstorms over the period (particularly the documented step change in 2012, although I'd imagine there must have been other smaller changes over the period) make it a little hard to judge what actual degree of change there was in their size, latitude, and incidence.
Does anyone know more about the source of this data, and to what extent our ability to detect thunderstorms up there has changed?

From a children's book: "In The Legend of Lightning and Thunder, a traditional legend that has been told in the Kivalliq region of Nunavut for centuries, two siblings resort to stealing from their fellow villagers, and inadvertently introduce lightning and thunder into the world. This beautiful...

It seems like a very interesting shift. However, the increase in ability to detect arctic thunderstorms over the period (particularly the documented step change in 2012, although I'd imagine there may have been other smaller changes over the period) make it a little hard to judge what actual degree of change there was in their size, latitude, and incidence.
Does anyone know more about the source of this data, and to what extent our ability to detect thunderstorms up there has changed?

From a children's book: "In The Legend of Lightning and Thunder, a traditional legend that has been told in the Kivalliq region of Nunavut for centuries, two siblings resort to stealing from their fellow villagers, and inadvertently introduce lightning and thunder into the world. This beautiful...

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has...

@Colorado Bob,
Indeed. With 1.5 million hectares burnt in the USA (mainly Alaska) so far this year and 2.4 million hectares burnt in Canada (principally Saskatchewan but generally all over the north and west of the country), and no end in sight on either side of the border, this looks like a big year for wildfires.

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has...

So an atypical year, with lots of ice melting in situ but very little export.
@Jim Hunt,
Those wildfires may not be Alaskan. Millions of hectares have been ablaze in Canada too.
http://www.ciffc.ca/index.php?option=com_content&task=view&id=25&Itemid=27

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has...

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has...

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has...

@Bill,
The discussion was a long and messy one in the comments on a blog article... somewhere. I remember they based their argument on this graph (or at least the most recent part of it) though: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has...

I won't be hoping for unambiguous proof myself, jdallen. Particularly given how many people report their beliefs actually being strengthened by contradictory evidence.
Also, ice area and extent have so much noise and so many disparate measures as indicators that people can easily interpret it selectively and seize on apparently contradictory "evidence"; the latest one that sceptics have been wheeling out in debate is that global sea ice area has been equal to the 1979-2008 average for the past two years (http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg).
Never mind that they liked to completely ignore it for the previous two years, when it was well below said average, or that if you drew a regression line through the whole history, it would go down :S

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2014 period (NSIDC has...

Let's have an alternative, shorter term betting game: is this downwards pre-melt season trend in declining sea ice cover going to carry on, flatten out, or bounce back a little?
Please make your predictions between now and the 15th of March as to the sea ice extent (NSIDC) on 01.04.2015. Whoever guesses closest to the actual amount wins the prize of one virtual cookie.
I'm going to start the guessing game at a nice, round, 14.00 million square km. (A bit of a drop further from where it is now, but not much).

Okay, I'm not calling the max - short for maximum extent of the sea ice pack that marks the end of the freezing season - as I've sworn not to do that anymore since 2012, when I called the max twice, only to see the trend line bounce up higher and later. But this year something really interestin...

Going to try not to get too exciting about this myself, as we're still in the lower-insolation half of the year.
(But I know I'll be checking back come the equinox in 11 days time to see if we're still at record-breakingly low levels :) )

Okay, I'm not calling the max - short for maximum extent of the sea ice pack that marks the end of the freezing season - as I've sworn not to do that anymore since 2012, when I called the max twice, only to see the trend line bounce up higher and later. But this year something really interestin...

@NJSnowFan,
We looked into the potential impact of increased ship traffic, including but not limited to ice breakers, over on the sea ice forums, and based on some basic number-crunching it really didn't look like they could account for very much of the melt.
@Hans Verbeek
"Anyway, it costs a lot of diesel fuel to break up Arctic seaice. Peakoil will also mean peak-icebreaker. ;-)"
Not necessarily; the biggest ones are nuclear-powered.

During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily Cryosphere Today sea ice area (SIA) and IJIS sea ice extent (SIE) numbers, which I compare to data from the 2005-2012 period (NSIDC has ...

@Pete,
5.632 million square km as of August 27th (you can see the most recently reported extent by scrolling over this graph: http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/).
I now reckon we were way out, and the September average will be about 5 to 5.3 million square km.

In mid-July through early August, participants on the Arctic Sea Ice (ASI) blog posted 66 individual predictions for the mean NSIDC September Arctic sea ice extent. The median value of these 66 predictions is 3.6 million km2, with an interquartile range (approximately the middle 50%) from 2.92 t...

@John,
I completely agree. I wouldn't expect to see zero ice in winter at any point in the next hundred years - months of sunless winter are sure to freeze at least a thin layer of the ocean surface, even if the amount formed continues to slowly fall, and melts away earlier each year. Even if arctic temperatures went up 10 degrees celsius, they'd still be regularly going below -30 degrees. So why would the ice stop forming?

In mid-June through early July, participants on the Arctic Sea Ice (ASI) blog posted 82 individual predictions for the mean NSIDC September Arctic sea ice extent. The median value of these 82 predictions was 3.2 million km2, with an interquartile range (approximately the middle 50% of prediction...

Does anyone know what impact the increased shipping, drilling, harbour investment, fishing and other activity as the ice melts is expected to have on the rate at which what ice is left declines? Because such activity should probably start rising to a peak now... and I have to wonder if this particular positive feedback mechanism may not have been one of the reasons last year's melt went on as long as it did.

In mid-June through early July, participants on the Arctic Sea Ice (ASI) blog posted 82 individual predictions for the mean NSIDC September Arctic sea ice extent. The median value of these 82 predictions was 3.2 million km2, with an interquartile range (approximately the middle 50% of prediction...

4.2m again.
PIOMAS volume seems to be lagging a long way behind the last couple of years, meaning a big catch-up would be needed to get close to last year. But with all that first year ice, there should still be a big melt to come... so I'm still betting it'll reach 2nd place, if only barely. (BTW, I really don't know all that much about what I'm talking about).

In mid-June through early July, participants on the Arctic Sea Ice (ASI) blog posted 82 individual predictions for the mean NSIDC September Arctic sea ice extent. The median value of these 82 predictions was 3.2 million km2, with an interquartile range (approximately the middle 50% of prediction...

This comment by long-time commenter Rob Dekker was so good and elegant that I decided to squeeze it in as a follow-up guest blog to the first Problematic predictions post. ----- In Bill's excellent overview of correlations here, he used 'area' earlier as a predictor for 'area' later (area->are...

This comment by long-time commenter Rob Dekker was so good and elegant that I decided to squeeze it in as a follow-up guest blog to the first Problematic predictions post. ----- In Bill's excellent overview of correlations here, he used 'area' earlier as a predictor for 'area' later (area->are...

@Mdoliner,
Even though it's been rare in the past, I wouldn't count out a possible volume increase this year, since when last reported, the PIOMAS ice volume was tracking "425 and 901 km3 above those of 2011 and 2012 respectively": http://neven1.typepad.com/blog/2013/06/piomas-june-2013.html.

Each June, July and August, the SEARCH Sea Ice Outlook (SIO) collects predictions for the mean extent of Arctic sea ice in September. These predictions come mainly from scientists but also some other people, drawing on a variety of modeling, statistical or subjective methods that each contributo...

I feel we could do with a little more discussion of the extent of our individual uncertainties. Personally, I'd be very surprised if the extent this year was either less than 2.6 million sq km (a drop of more than 1 million sq km from 2012's record, and a very steep drop from where we stand today), or more than 5.1 million sq km (ie, more than any year since 2007, and a rise of more than 1.5 million sq km from 2012). But anything in between seems possible, especially with the great uncertainty and disagreement about what the implications of the cyclone's behaviour might actually be.

Each June, July and August, the SEARCH Sea Ice Outlook (SIO) collects predictions for the mean extent of Arctic sea ice in September. These predictions come mainly from scientists but also some other people, drawing on a variety of modeling, statistical or subjective methods that each contributo...

Each June, July and August, the SEARCH Sea Ice Outlook (SIO) collects predictions for the mean extent of Arctic sea ice in September. These predictions come mainly from scientists but also some other people, drawing on a variety of modeling, statistical or subjective methods that each contributo...

4.2 million square kilometres.
This is an adjustment upwards of 0.5 million square kilometres from my prior prediction of 3.7 million square kilometres, based on the slow start to the melt season. However, it would still be the second lowest on record...

Each June, July and August, the SEARCH Sea Ice Outlook (SIO) collects predictions for the mean extent of Arctic sea ice in September. These predictions come mainly from scientists but also some other people, drawing on a variety of modeling, statistical or subjective methods that each contributo...

3.7 million square km. (+/- 1 million square km).
I'm guesstimating that it'll be about the same as last year based on current PIOMAS volume, NSIDC extent and Cryosphere area being about the same this year as last year, and based on general drivers not changing that much year-to-year. Put me down as an optimist, I suppose.

How does the collective wisdom of Arctic Sea Ice blog participants compare with expert scientific analysis in forecasting the September sea ice extent? This question seems worth exploring with a crowd-source experiment. You are all invited to submit, as comments to this post, your best guess for...

@Bosbas, Crandles,
Thank you for your responses.
If the lower average monthly ice extent for past years is indeed because ice has been more mobile in 2012, and thus seemed more extensive over the course of a month, then it would indeed seem to explain it.
And if that is the explanation, then personally, I think it makes sense to place more emphasis on the daily figures, representing the extent of sea covered by ice at any one time, rather than on the monthly figures which would instead seem to represent the extent of where the ice has been. But that may just be my bias talking...

I doubt this is the end of the record streak, but as we approach the end of the year, this will probably be the final record domino of 2012. And what a fitting number to end it with! The record fell over three weeks ago (see data). The reason I'm reporting it now is not just because I'm lazy o...

@P-maker,
I am indeed pretty dubious of the metric in question - it seems to have been seized upon by some sceptics simply because it is a "last hold-out", as it were. But if it looks like it'll fall soon enough, it's one more bit of debating ground they'll have to abandon.
@crandles,
One thing I don't get from the nsidc data in the latest bit of Arctic Sea Ice News. Based on Figure 2, November ice extent seems to track lowest in 2012 for most of the month, and 2012 seems to clearly be the lowest in average overall, but in Figure 3 it's only the third lowest November on average. Do you know if there's some difference in how the extent figures are calculated across the two different graphs?
(I noticed something similar in the previous installment, but it wasn't quite so stark a contrast as in this month's).

I doubt this is the end of the record streak, but as we approach the end of the year, this will probably be the final record domino of 2012. And what a fitting number to end it with! The record fell over three weeks ago (see data). The reason I'm reporting it now is not just because I'm lazy o...